Description of the Prior Art
This invention, in its preferred form, relates to apparatus and a related method for assembling inner grid straps so as to form a grid of generally square configuration, and for providing outer grid straps on the grid formed from the inner grid straps. More particularly, the invention relates to (a) a grid assembly fixture for holding a first set of inner grid straps in parallel relationship, and for holding a second set of grid straps parallel to each other and perpendicular to the straps of the first set, and for holding outer grid straps, (b) to a retention strap for retaining the grid formed of the inner and outer grid straps in assembled relationship, and (c) to a method of assembling a grid from grid straps using the grid assembly fixture and retention strap.
Nuclear fuel bundle assemblies include a matrix of nuclear fuel rods which are arrayed in rows and columns, and which are held in the desired configuration by a plurality of fuel rod grids. These grids are produced from "straps" which are linearly extending, generally rectangular elements, characterized by having slots extending from one edge approximately half way through the depth of the strap. The straps are assembled so that one strap is in mating relationship with the other strap. Thus, the slot of one strap engages the other strap at a portion thereof which is in alignment with the slot of that other strap, with the result that the grid is of the same depth as each of the straps which forms the grid. The resulting grid has a first set of straps which are substantially parallel to each other, and equally spaced, and a second set of straps which are parallel to each other and equally spaced, the straps of one set being perpendicular to the straps of the other set. All of the aforesaid straps are designated as "inner straps", and they are placed in mating relationship to form a square grid of square cells, in the above noted rows and columns. In addition, there are provided outer straps, which are placed on the four sides of the grid.
The inner straps and outer straps were formerly assembled by first joining together two straps in mating relationship on a conventional table or plate. Typically, two additional straps were added, so that there resulted the four outer-most inner straps, which thereby formed a frame. The remaining inner straps were then placed in position, utilizing the frame provided by these first four placed straps. Then the outer straps where placed in position, and an encircling strap or holding strap was placed about the entire assembled grid. Further processing was then effected by placing brazing material at various locations on the grid, and the grid with the brazing material placed on it was then positioned in an oven, where brazing was effected.
The above-described method and related apparatus resulted in a very time consuming operation.